1. Field of the Invention
The present invention relates to a press-button switch, and more particularly, to a switch which makes use of a push element and a hook member at the side of the switch to rotate a rotary body in a single direction, thereby causing a push-pull rod to move upwards and downwards in an eccentric way so that the switch can change between on state and off state. In addition, the press-button switch can be smoothly disconnected in off state for ensuring the electric safety in case of overload current.
2. Description of the Prior Art
The kinds of switches are various. The common ones are, for example, seesaw switch, press-button switch, etc. In earlier period, they only have on-off function. In case of overload current, they are not able to be disconnected, thereby causing the electric danger in use. Therefore, a safety switch with automatic shutdown device was developed. The inventor of the present invention owns over ten patents in this field. However, the safety switch in the earlier period is mainly the type of seesaw switch while only few press-button switches are provided with automatic shutdown device due to the restriction of the internal construction.
FIGS. 1(A) and 1(B) show a safety see-saw switch 1 disclosed in Taiwanese Patent No. 320355 by the inventor of the present invention in which the on-off control is performed by the up-and-down movement of the press-button 11. In case of the overload current of the conductive strip 12, an automatic shutoff of the switch is achieved.
Since the press-button switch is more suitable for use in computers and electrical appliances, the press-button switch with automatic shutdown device for overload current began to be developed.
FIGS. 2(A) and 2(B) show a safety press-button switch disclosed in Taiwanese Patent No. 422404. This safety press-button switch includes a housing 21, a press button 22 and an actuating piece 23. The press button 22 and the actuating piece 23 are integrated in a body. The present invention is characterized in that the actuating piece 23 has a heart-like locating groove 24. A terminal 25 at the right side is connected with a metal engaging piece 26 made of double material and provided with an engaging projection 261 in such a way that the interconnection between terminals are achieved. In case of overload current, a great heat is produced and transmitted to the metal engaging piece 26 through the right terminal 25 so that the metal engaging piece 26 is, after being heated, bent to the right side to be separate from engagement. In addition, the press button 22 is raised by means of the main spring 27 in the off state. However, the above-mentioned construction is not optimal, or even inapplicable. As shown in FIG. (B), when the contact points 281, 251 of the middle terminal 28 and the right terminal 25 are in contact with the contact points 291, 292 of the arched seat 29 in lowering the arched seat 27, the overload current is effected upon the middle and right terminals 28, 25 and the arched seat 29, rather than directly upon the metal engaging piece 26. Accordingly, it""s too late for the metal engaging piece 26 to be deformed for disconnection when the heat created in case of short circuit is transmitted from the arched seat 29 to the right terminal 25 and further to the metal engaging piece 26, thereby causing the electric danger in use.
Moreover, the aforementioned has to use four contact points 281, 291, 292, 251. In comparison with another switches with two contact points, it""s not a practical design.
Referring to FIGS. 3(A), 3(B) and 3(C), a further press-button switch disclosed in the Taiwanese Patent No. 458362 comprises:
a housing 31 being hollow inside and having an opening 311 divided into two operating rooms 313, 314 by a separation member 312, a press button assembly 32 and a conducting assembly 33 being arranged within the operating rooms 313, 314, said conducting assembly 33 being connected with a switching assembly 35; and
a coupling mechanism 34 having a press element 341 disposed in the operating area and plugged into a through hole 311 of the separation member 312, a resilient element 342 connected to the press element 341 and the separation member, and a rotary seat 344 pivotably connected to the housing and provided with a guide groove 343 for receiving the press element 341 in the rotary seat 344, said rotary seat 344 further having a locating part 345 in connection with the switching assembly 35.
Based upon the above-mentioned, the press element 341 is pressed downwards by the press button assembly 32, and the resilient element 342 is compressed so that the other end of the press element 341 is pressed against the guide groove 343 in such a way that the rotary seat 344 is deflected to move the switching assembly 35 and to enable the conducting assembly 33 in connection state. Besides, the press button assembly 32 and the press element 341 restores itself back to its original position by means of the resilient element 342 so that a press-button switch is created.
However, the upper part (I) of the above-mentioned configuration is formed as a conventional press-button switch while the lower part (II) thereof is formed as a conventional seesaw switch. This is only an improvement of Taiwanese Patent No. 83365 (U.S. Pat. No. 5,262,748). Based upon the U.S. Pat. No. 5,262,748, the press button assembly 32 is added to the top of the housing 31 while the rotary seat 344 is the see-saw press button of U.S. Pat. No. 5,262,748. Accordingly, the Taiwanese Patent No. 458362 has a too complicated construction so that the assembly is difficult and its cost is high. Moreover, too many components lead to a high malfunction rate. Consequently, it""s applicable, but not perfect and practical.
It is a primary object of the present invention to remove the above-mentioned drawbacks of the conventional press-button switch and to provide a press-button switch which has simple components so that it""s easy for assembly.
It is another object of the present invention to provide a press-button switch which has low production cost and malfunction rate.
It is a further object of the present invention to provide a press-button switch which has the automatic shutoff function in case of overload current for ensuring the electric safety.